Increasing road traffic and corresponding congestion has various negative effects. Accordingly, efforts have been made to combat increasing traffic congestion in various ways, such as by making information about current traffic conditions available. Such current traffic information may be provided to interested parties in various ways (e.g., via radio broadcasts, an Internet Web site that displays a map of a geographical area with color-coded information about current traffic congestion on some major roads in the geographical area, information sent to cellular telephones and other portable consumer devices, etc.). One source for information about current traffic conditions includes observations manually supplied by humans (e.g., traffic helicopters that provide general information about traffic flow and accidents, reports called in by drivers via cell phones, etc.), while another source in some larger metropolitan areas is networks of traffic sensors capable of measuring traffic flow for various roads in the area (e.g., via sensors embedded in the road pavement). Unfortunately, various problems exist with respect to such information, such as related to the accuracy and coverage of the information, as well as to similar information provided by other sources.
One use of road traffic information includes providing the road traffic information to drivers of vehicles, such as to notify drivers of recent road traffic on particular roads of interest. In addition, automated navigation systems may use information about roads in various manners, including to generate and display a route between two indicated locations. However, various problems exist with current navigation systems and other current techniques for determining routes.